Update Child records help Scripting

I would like to know if anyone can help me with figuring out how to update secondary records. 

I have the following script that will update the parent record (all records are parent unless the parent field is filled in)  I need to find all secondary records and set the u_triage_sla_time on them.  But not sure how to accomplish that.

(function executeRule(current, previous /*null when async*/) {

	var parentID = current.sys_id;
	var tableName = 'em_alert';
	//var assignedTo = current.u_assigned_to;
	
	var gdt = new GlideDateTime(new Date());
		
	var emAlert = new GlideRecord(tableName);
	emAlert.addQuery('sys_id',parentID);
	emAlert.query();
    while (emAlert.next()){
		//gs.info('@@@ UpdateTriageTime completed at ' + gdt);
		emAlert.setValue('u_triage_sla_time',gdt);
		emAlert.update();
	}
	
	

})(current, previous);

Need to do with this script:

1.  Find any other record in the em_alert table that has the parent field the same as the current sys_id (all child records) I can do the update part just need to know how to find all child (secondary) alerts.